1. Field of the Invention
The present invention relates to a system for inspecting and mending welded parts and heat-affected zones of a reactor vessel and internal structures thereof, particularly to an inspection and mending system preferably used in places of a wide region to which the entrance of access is very narrow.
2. Description of the Related Art
A conventional inspection apparatus for the welded parts of an outer surface of a shroud in a reactor vessel is described in Japanese Patent Application Laid-Open No. 116747/1990.
A conventional mending apparatus for an inner surface of a shroud in a reactor vessel is described in Japanese Patent Application Laid-Open No. 80186/1993.
In the former conventional inspection apparatus, only inspection of the welded part at the inner face of a reactor vessel is executed but mending of the welded parts based on the inspection results is not presented.
Downsizing of the inspection or the mending apparatus is required since the space outside the shroud of the reactor vessel is very narrow. The inspection at the narrow space is comparatively easy since only insertion of a probe is needed. However, as for the mending apparatus, there has been a problem that the defect can not be mended since downsizing of the mending apparatus is difficult and the mending apparatus hardly gets near the defect even if a defect is detected. In order to avoid the problem, it is necessary to use the mending apparatus from the inside of the shroud but this mending method is difficult in case visual observation of the defect is not possible and positioning at the place to be mended is difficult. Positioning the mending apparatus at the maintained place by visual observation is impossible if the defect is not considerably large.
The latter conventional mending apparatus has a problem that its positioning is difficult since vibration by deflection of its arm with more than 3 m of length occurs in movement of the arm and three-dimensional positioning is further needed in every movement of the arm.
Furthermore, the conventional inspection and the conventional mending apparatus can not get near the inner face of the shroud or the shroud support if the apparatus can not pass through a hole of the upper grid or the core support plate when occasion demands. Therefore, each of the apparatuses needs to be independently composed since the size of those apparatuses must be designed in a smaller size than the hole width of the upper grid. And another problem is that it is difficult to transfer the defect position data detected by the inspection apparatus to the mending apparatus in maintenance by the conventional inspection and the conventional mending apparatus, which makes the mending of the detected defect very difficult.